The present invention relates generally to fluid centrifuges that are constructed and arranged to separate particulate matter from a supply of fluid. More specifically, the present invention pertains to a fully disposable, molded plastic centrifuge rotor that is constructed and arranged without the need to use any metallic bushings or other metallic parts or components.
One consideration in the design and/or redesign of fluid processing and fluid filtering components, such as a centrifuge rotor, is whether the component(s) can be constructed and arranged so as to be nonmetallic or at least predominantly nonmetallic. A component design or assembly design that is predominantly nonmetallic, preferably all plastic, is considered to be “disposable” since it can be incinerated for disposal or it can be recycled, depending on the selected materials. By providing a component construction that is incinerateable, the structural mass of the component(s) can be reduced to low volume ash and this limits what will be added to landfills. The other option for “disposal” is to recycle the plastics used in the construction of the component(s) or assembly. Presently, when there is a construction for fluid processing and fluid filtering components that is substantially all plastic, the components or the assembly or subassembly of those components is described as having an environmentally friendly, “green” design.
A further aspect of redesigning components in order to achieve an all-plastic construction is the elimination of metallic parts that typically represent a higher cost compared to the plastic replacement. When it is possible to mold the replacement part or feature as part of another existing component, then it is possible to eliminate one or more assembly steps and this represents a cost savings in terms of labor.
One of the applications for an all-plastic construction is in the design of a centrifuge rotor. One current design that includes a stack of particulate separator cones within the rotor includes metal bushings that are pressed into the plastic rotor housing. At each oil change, when the rotor is discarded, the metal bushings are also discarded, even though they have only seen less than five percent (5%) of their useful life. Additionally, these metal bushings have to be pressed out of the rotor housing before the rotor can be incinerated. The desire for a fully disposable, “green” product and concerns over costs related to the metal bushings have driven the conception of the present invention. By eliminating the metal bushings, the cost of the component parts is saved as well as eliminating the labor time to press the bushings into the rotor housing and to press them out of the housing before disposing of the rotor.
An improvement related to the elimination of all metal bushings from the centrifuge rotor, according to the present invention, is the design and use of a molded plastic rotor shaft spud as a unitary portion of an upper rotor portion. A similar molded plastic rotor shaft spud is provided as a unitary portion of a baseplate component, comprising part of the centrifuge rotor. These rotor shaft spuds provide the rotor/bearing surfaces for rotation of the centrifuge rotor relative to the centrifuge shell or housing. When these rotor shaft spuds are unitarily molded as a symmetrical part of a larger component, i.e., the upper rotor portion and the baseplate, potential out-of-roundness concerns can be minimized.